Eight of the patients who received two doses of mRNA-1273 — one at 25 micrograms and the other at 100 — developed neutralizing antibodies similar to the ones developed by people who’ve recovered from the virus.

"These interim Phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25 µg,” Moderna’s Chief Medical Officer Dr. Tal Zaks said in a news release.

Moderna said mRNA-1273 was “generally safe and well-tolerated.” The only adverse effect Moderna noted was a single patient who developed redness around the injection site.

“When combined with the success in preventing viral replication in the lungs of a pre-clinical challenge model at a dose that elicited similar levels of neutralizing antibodies, these data substantiate our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for pivotal trials,” Zaks said.

On May 6, the Food and Drug Administration gave its approval for Moderna to enter Phase 2 in its study of mRNA-1273.

Just six days later, the FDA granted it a “fast-track” destination, which will help accelerate the development of an effective vaccine.

A view of Moderna headquarters on May 08, 2020 in Cambridge, Massachusetts. Moderna was given FDA approval to continue to phase 2 of Coronavirus (COVID-19) vaccine trials with 600 participants. (Photo by Maddie Meyer/Getty Images)

Based on the Phase 1 results, the second phase will be amended to study 50-micrograms and 100-microgram doses.